See: Undo's answer to a previous meta question on this topic.
In that answer, Undo sets out what he thinks we should do with low-quality or off-topic questions - along similar principles to Gilles, who has the accepted answer. In essence, it comes down to "close questions, delete answers" if they don't match our requirements.
At the moment, we haven't had any problems with that policy, so I'd be heavily inclined to keep doing that. Closing questions but not deleting them allows for editing and reopening that can't happen when deleted (except by mod intervention - there just aren't enough voters with the rep).
I'd also be wary of pre-empting the roomba's deletions - the time limits set on those are (presumably) set at the lengths they are for a reason, so I'd be careful of deleting those early unless they deserve it for some other reason.